Control method and control device of low-temperature rectification system

Abstract

The invention provides a control method and a control device of a low-temperature rectification system. The control method comprises the following steps: controlling a first-stage rectification tower and a second-stage rectification tower to be in a preset vacuum state; collecting process parameter signals of the first-stage rectifying tower and the second-stage rectifying tower, wherein process parameters comprise at least one of temperature, pressure, flow, power and gas concentration; performing programming conversion on the process parameter signal to obtain process parameter data, and displaying the process parameter data; and adjusting the operation states of the primary rectifying tower and the secondary rectifying tower based on the process parameter data. According to the control method provided by the embodiment of the invention, the process parameters of the first-stage rectifying tower and the second-stage rectifying tower are monitored in real time and integrally regulated and controlled through the PLC control system, so that the low-temperature rectifying system is in a stable working state, the stability of the low-temperature rectifying tower is improved, and the low-temperature rectifying process requirements are met.

Description

Technical Field

[0001] The present application relates to the technical field of cryogenic distillation, and in particular to a control method and a control device of a cryogenic distillation system. Background Art

[0002] The cryogenic distillation process uses the differences in boiling points of the raw gas components at specific temperatures and pressures to separate the light and heavy components.

[0003] In the related art, the cryogenic distillation tower of the cryogenic distillation system has multiple controlled variables and multiple manipulated variables, which makes the control of the cryogenic distillation tower by the cryogenic distillation system more complicated and has a large hysteresis. Summary of the invention

[0004] In view of this, the embodiments of the present application hope to provide a control method and a control device for a cryogenic distillation system, so as to simplify the control of the cryogenic distillation system and improve the stability of the operation of the cryogenic distillation system.

[0005] To achieve the above object, one aspect of an embodiment of the present application provides a control method for a cryogenic distillation system, the control method being based on a programmable logic controller, the cryogenic distillation system comprising a primary distillation tower and a secondary distillation tower, the control method comprising:

[0006] Controlling the primary distillation tower and the secondary distillation tower to be in a preset vacuum state;

[0007] Collecting process parameter signals of the primary distillation tower and the secondary distillation tower, wherein the process parameters include at least one of temperature, pressure, flow rate, power, and gas concentration;

[0008] Performing programming conversion on the process parameter signal to obtain process parameter data, and displaying the process parameter data;

[0009] Based on the process parameter data, the operating states of the primary distillation tower and the secondary distillation tower are adjusted.

[0010] In some embodiments, before collecting the process parameter signals of the primary distillation tower and the secondary distillation tower, the control method includes:

[0011] Passing raw gas into the primary distillation tower;

[0012] After the primary distillation tower is in a saturated state, stop introducing the raw gas into the primary distillation tower, and control the operation of the condenser and the reboiler corresponding to the primary distillation tower to obtain the first gas;

[0013] introducing the first gas into the secondary distillation tower;

[0014] After the secondary distillation tower is in a saturated state, the introduction of the first gas into the secondary distillation tower is stopped, and the operation of the condenser and the reboiler corresponding to the secondary distillation tower is controlled to obtain the second gas.

[0015] In some embodiments, before the feed gas is introduced into the primary distillation tower, the control method includes:

[0016] The adsorption column of the cryogenic distillation system is controlled to adsorb gas impurities in the raw gas.

[0017] In some embodiments, the control method includes:

[0018] When the amount of gas filtered by the adsorption column exceeds a preset value or when the feed gas stops passing into the primary distillation tower, controlling the temperature of the adsorption column to increase so as to regenerate the adsorption column;

[0019] Introducing nitrogen into the adsorption column to bring gas impurities into the absorption tank;

[0020] The temperature signal of the adsorption column is collected to determine whether the temperature signal is within a preset range, and if not, an alarm message is output.

[0021] In some embodiments, controlling the primary distillation tower and the secondary distillation tower to be in a preset vacuum state includes:

[0022] collecting vacuum signals of the primary distillation tower and the secondary distillation tower;

[0023] Performing program conversion on the vacuum signal to obtain vacuum data, and displaying the vacuum data;

[0024] Based on the vacuum data, it is determined whether the primary distillation tower and the secondary distillation tower are in the preset vacuum state.

[0025] In some embodiments, collecting the process parameter signals of the primary distillation tower and the secondary distillation tower includes:

[0026] Collecting temperature signals of condensers and / or reboilers corresponding to the primary distillation tower and the secondary distillation tower respectively;

[0027] collecting temperature signals of the primary distillation tower and the secondary distillation tower;

[0028] The step of programming and converting the process parameter signal to obtain process parameter data and displaying the process parameter data comprises:

[0029] Controlling the temperature display module to display the temperature signal of the condenser and / or the reboiler;

[0030] Performing programming conversion on the temperature signal to obtain temperature data of the condenser and / or the reboiler, and displaying the temperature data of the condenser and / or the reboiler;

[0031] Controlling the thermal resistance module to receive the temperature signals of the primary distillation tower and the secondary distillation tower;

[0032] Performing program conversion on the temperature signal to obtain temperature data of the primary distillation tower and the secondary distillation tower, and displaying the temperature data of the primary distillation tower and the secondary distillation tower;

[0033] The adjusting the operating states of the primary distillation tower and the secondary distillation tower based on the process parameter data includes:

[0034] Based on the temperature data of the condenser and / or the reboiler, the operating states of the primary distillation tower and the secondary distillation tower are adjusted.

[0035] In some embodiments, adjusting the operating status of the primary distillation tower and the secondary distillation tower includes:

[0036] The powers of the reboilers corresponding to the primary distillation tower and the secondary distillation tower are adjusted.

[0037] In some embodiments, the cryogenic distillation system includes a plurality of gas flow controllers, which are arranged at least between the primary distillation tower and the adsorption column, between the primary distillation tower and the absorption tank, between the primary distillation tower and the secondary distillation tower, between the secondary distillation tower and the product tank, and between the secondary distillation tower and the absorption tank. The absorption tank is used to store nitrogen and gas impurities, and the product tank is used to store the gas obtained after distillation.

[0038] The collecting of process parameter signals of the primary distillation tower and the secondary distillation tower comprises:

[0039] Collecting flow signals from each of the gas flow controllers;

[0040] The step of programming and converting the process parameter signal to obtain process parameter data and displaying the process parameter data comprises:

[0041] Performing program conversion on the gas flow signal to obtain gas flow data, and displaying the gas flow data;

[0042] The adjusting the operating states of the primary distillation tower and the secondary distillation tower based on the process parameter data includes:

[0043] Adjust the gas flow controller.

[0044] In some embodiments, collecting the process parameter signals of the primary distillation tower and the secondary distillation tower includes:

[0045] Collecting liquid level signals of reboilers corresponding to the primary distillation tower and the secondary distillation tower;

[0046] The step of programming and converting the process parameter signal to obtain process parameter data and displaying the process parameter data comprises:

[0047] Performing programming conversion on the liquid level signal to obtain liquid level data, and displaying the liquid level data;

[0048] The adjusting the operating states of the primary distillation tower and the secondary distillation tower based on the process parameter data includes:

[0049] The powers of the reboilers corresponding to the primary distillation tower and the secondary distillation tower are adjusted.

[0050] Another aspect of the present application provides a cryogenic distillation control device, which is applied to the control method of the cryogenic distillation system described in any one of the above, and the cryogenic distillation control device includes:

[0051] A collection module, used for collecting process parameter signals of the cryogenic distillation system;

[0052] A data conversion module, used for converting the process parameter signal into process parameter data;

[0053] A display module, used to store and display the process parameter data and output an alarm signal for abnormal data;

[0054] The regulating module is used to regulate the operation of the primary distillation tower and the secondary distillation tower according to the process parameter data.

[0055] The control method of the cryogenic distillation system provided in the embodiment of the present application is aimed at the existing cryogenic distillation system. Through the PLC control system, the process parameters of the primary distillation tower and the secondary distillation tower are monitored in real time and overall regulated, so that the cryogenic distillation system is in a stable working state, the stability of the cryogenic distillation tower is improved, and the requirements of the cryogenic distillation process are met. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 A schematic flow chart of a control method for a cryogenic distillation system provided in one embodiment of the present application;

[0057] Figure 2 A schematic flow chart of a control method for a cryogenic distillation system provided in another embodiment of the present application;

[0058] Figure 3 This is a schematic diagram of the structure of the cryogenic distillation system controlled by the control method of this application.

[0059] Description of Reference Numerals

[0060] 10. Cryogenic distillation system; 11. Adsorption column; 12. Primary distillation tower; 13. Secondary distillation tower; 14. First condenser; 15. First reboiler; 16. Second condenser; 17. Second reboiler; 18. Absorption tank; 19. Product tank; T1. First temperature sensor; T2. Second temperature sensor; T3. Third temperature sensor; T4. Fourth temperature sensor; T5. Fifth temperature sensor; T6. Sixth temperature sensor; T7. Seventh temperature sensor; T8. Eighth temperature sensor; T9. Ninth temperature sensor ; T10, the tenth temperature sensor; T11, the eleventh temperature sensor; T12, the twelfth temperature sensor; T13, the thirteenth temperature sensor; L1, the first liquid level sensor; L2, the second liquid level sensor; F1, the first gas flow controller; F2, the second gas flow controller; F3, the third gas flow controller; F4, the fourth gas flow controller; F5, the fifth gas flow controller; P1, the first pressure sensor; P2, the second pressure sensor; P3, the third pressure sensor; P4, the fourth pressure sensor. DETAILED DESCRIPTION

[0061] The following is a further detailed description of the implementation of the present application in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present application but cannot be used to limit the scope of the present application.

[0062] In the description of the embodiments of the present application, it should be noted that the orientations or positional relationships indicated by the terms "upper", "lower", "top", "bottom", "inner", etc. are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the embodiments of the present application. In addition, the terms "first", "second", "third", etc. are used only for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0063] In the description of the embodiments of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific circumstances.

[0064] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiments of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0065] The cryogenic distillation process uses the differences in boiling points of the raw gas components at specific temperatures and pressures to separate the light and heavy components.

[0066] In the related art, the cryogenic distillation tower of the cryogenic distillation system has multiple controlled variables and multiple manipulated variables. Cryogenic distillation is a complex control process with large hysteresis. Reasonable selection of variables for control is conducive to reducing the correlation of the system and maintaining stable operation.

[0067] Based on the above situation, the first aspect of the embodiment of the present application provides a control method of a cryogenic distillation system 10. Figures 1 to 3 The control method is based on a programmable logic controller. The cryogenic distillation system 10 includes a primary distillation tower 12 and a secondary distillation tower 13, and the control method includes:

[0068] S100: Control the primary distillation tower and the secondary distillation tower to be in a preset vacuum state;

[0069] S200: collecting process parameter signals of the primary distillation tower and the secondary distillation tower, wherein the process parameters include at least one of temperature, pressure, flow rate, power, and gas concentration;

[0070] S300: performing programming conversion on the process parameter signal to obtain process parameter data, and displaying the process parameter data;

[0071] S400: Based on the process parameter data, the operating states of the primary distillation tower and the secondary distillation tower are adjusted.

[0072] It should be noted that the cryogenic distillation system 10 is a process system utilizing cryogenic distillation, also known as cryogenic separation.

[0073] Cryogenic distillation is a gas liquefaction technology that utilizes the difference in boiling points of different gases in a mixed gas to cool and liquefy the mixed gas under high pressure, thereby achieving the purpose of separating the mixed gas. It can be understood that separating the mixed gas can also be understood as purifying a gas dominated by a certain component.

[0074] Illustratively, the embodiment of the present application purifies a gas mainly composed of boron trifluoride (BF3), so that high-purity boron trifluoride gas can be obtained through low-temperature distillation.

[0075] Boron trifluoride (BF3) is a very important basic fluorinated boride, which is widely used in industry. In the metallurgical industry, boron trifluoride is a flux used for magnesium welding, a lubricant for cast steel, and a component of boron treatment agent for steel or other metal surfaces; in the chemical industry, it is mainly used as an organic reaction catalyst, and is also the main raw material for the preparation of boron halides, elemental boron, borane and sodium borohydride. Its most important application is in the field of electronics and semiconductors. High-purity boron trifluoride is a P-type doping source for silicon and germanium epitaxy, diffusion and ion implantation processes. The chips produced have the characteristics of high integration, high density, small size and good performance. With the rapid development of the electronics industry, the requirements for the purity of boron trifluoride are also increasing.

[0076] It should be noted that the control method of the cryogenic distillation system 10 provided in the embodiment of the present application can be used to separate any gas.

[0077] During the cryogenic distillation process, the light component gas is usually gathered at the top of the cryogenic distillation tower of the cryogenic distillation system 10, and the heavy component gas is usually gathered at the bottom of the cryogenic distillation tower (usually in liquid state). The cryogenic distillation system 10 can collect the required components in the cryogenic distillation tower and process the unnecessary components according to actual needs.

[0078] Exemplarily, for the purification of boron trifluoride, the impurities in the low-purity boron trifluoride entering the cryogenic distillation tower of the cryogenic distillation system 10 are usually lighter than boron trifluoride. After low-temperature distillation in the cryogenic distillation tower, most of the impurities are accumulated at the top of the cryogenic distillation tower, and most of the boron trifluoride is accumulated at the bottom of the cryogenic distillation tower. In this way, in the cryogenic distillation system 10, boron trifluoride can be enriched at the bottom of the cryogenic distillation tower, and boron trifluoride with higher purity can be distilled out. Therefore, the purified boron trifluoride can be collected at the bottom of the cryogenic distillation tower, and the impurities can be collected and processed at the top of the cryogenic distillation tower.

[0079] It should be noted that the cryogenic distillation system 10 may have one or more cryogenic distillation towers, and the "multiple" mentioned in the embodiment of the present application refers to a number of two or more.

[0080] Among them, multiple cryogenic distillation towers of the cryogenic distillation system 10 are connected step by step, and the multiple cryogenic distillation towers can purify the gas step by step. For example, the gas purified in the primary distillation tower 12 is passed into the secondary distillation tower 13, and is further purified in the secondary distillation tower 13. The gas purified in the secondary distillation tower 13 is passed into the tertiary distillation tower, and is further purified in the tertiary distillation tower, and so on.

[0081] The embodiment of the present application is described by taking an example in which the cryogenic distillation system 10 includes two cryogenic distillation towers, namely, a primary distillation tower 12 and a secondary distillation tower 13 .

[0082] It should be noted that the control method of the present application is based on a programmable logic controller (PLC), which is used to collect and monitor various process parameters of the cryogenic distillation system 10 of the present application, and to control the cryogenic distillation system 10 of the present application.

[0083] PLC is used as the main controller, and the system hardware may include analog modules, digital modules, profibus-dp communication modules, Ethernet communication modules, safety barrier modules, low-temperature display modules, three-phase voltage regulator modules, etc. The software uses host computer monitoring software, so as to facilitate the collection and processing of process parameters such as temperature, pressure, flow, power, gas concentration, data and curve display, control parameter setting, data storage, signal alarm and interlocking of the cryogenic distillation system 10.

[0084] Among them, profibus stands for Process Field Bus, which is a process field bus communication protocol; DP stands for Decentralized Periphery, which is a profibus communication protocol running on a 485 serial port. profibus-dp is used for high-speed data transmission at the field level. The master station periodically reads the input information of the slave station and periodically sends output information to the slave station. The bus cycle time must be shorter than the master station (PLC) program cycle time. In addition to periodic user data transmission, profibus-dp also provides non-periodic communication required by intelligent devices for configuration, diagnosis and alarm processing.

[0085] In step S100, a vacuum unit composed of a mechanical pump and a molecular pump can be used to maintain a vacuum environment in the primary distillation tower 12 and the secondary distillation tower 13. Vacuuming during cryogenic distillation can reduce the impurity gas remaining in the primary distillation tower 12 and the secondary distillation tower 13, thereby improving the efficiency of cryogenic distillation and the purity of the product.

[0086] Exemplarily, the mechanical pump of the vacuum unit is started first, and when the mechanical pump evacuates the first distillation tower 12 and the second distillation tower 13 to a medium vacuum state, the molecular pump is started, and finally the first distillation tower 12 and the second distillation tower 13 are evacuated to a high vacuum state, and the high vacuum state in the first distillation tower 12 and the second distillation tower 13 is maintained.

[0087] For example, the mechanical pump is equipped with an electrical cabinet, which can realize the local / remote start and status indication of the mechanical pump. The mechanical pump is connected to the PLC digital input and output module through a hard line, and the basic functions such as pump start and stop, status feedback, and fault alarm are realized on the monitoring screen.

[0088] Exemplarily, the molecular pump is manually started and stopped on site according to the vacuum state in the distillation tower.

[0089] In step S200, one of the process parameters of temperature, pressure, flow rate, power, and gas concentration may be collected, or two, three, four, or all five of them may be collected, and there is no limitation here. By collecting these process parameters, data basis is provided for the subsequent control of the distillation tower.

[0090] In step 300, the process parameter signal is converted by programming so that the process parameter data can be obtained and displayed on the host computer, so that the PLC and the operator can monitor the process parameter signal.

[0091] In step 400, based on the obtained process parameter data, the cryogenic distillation system 10 is controlled by a PLC program so that the process parameters of the primary distillation tower 12 and the secondary distillation tower 13 are within a normal range, so as to maintain the stable operation of the cryogenic distillation system 10 and improve the stability of the cryogenic distillation system 10.

[0092] The control method of the cryogenic distillation system 10 provided in the embodiment of the present application is aimed at the existing cryogenic distillation system 10. Through the PLC control system, the process parameters of the primary distillation tower 12 and the secondary distillation tower 13 are monitored in real time and overall regulated, so that the cryogenic distillation system 10 is in a stable working state, the stability of the cryogenic distillation tower is improved, and the cryogenic distillation process requirements are met.

[0093] For some examples, see Figures 1 to 3 Before collecting the process parameter signals of the primary distillation tower 12 and the secondary distillation tower 13, the control method includes:

[0094] Feeding raw gas into the primary distillation tower;

[0095] After the primary distillation tower is in a saturated state, the feed gas to the primary distillation tower is stopped, and the operation of the condenser and the reboiler corresponding to the primary distillation tower is controlled to obtain the first gas;

[0096] introducing a first gas into a secondary distillation tower;

[0097] After the secondary distillation tower is in a saturated state, the introduction of the first gas into the secondary distillation tower is stopped, and the operation of the condenser and the reboiler corresponding to the secondary distillation tower is controlled to obtain the second gas.

[0098] It should be noted that the primary distillation tower 12 is in a saturated state, which means that the primary distillation tower 12 is filled with sufficient raw gas; similarly, the secondary distillation tower 13 is in a saturated state, which means that sufficient first gas is introduced into the secondary distillation tower 13, thereby improving the efficiency of cryogenic distillation.

[0099] Here, the gas concentration of the raw gas introduced into the primary distillation tower 12 can be detected to determine whether sufficient raw gas is introduced into the primary distillation tower 12, and the concentration of the first gas in the secondary distillation tower 13 can be detected to determine whether sufficient first gas is introduced into the secondary distillation tower 13. In this way, it can be determined whether to control the operation of the reboiler and condenser corresponding to the primary distillation tower 12 and the secondary distillation tower 13, respectively.

[0100] Among them, stopping the introduction of raw gas into the primary distillation tower includes:

[0101] Close the feed inlet and discharge outlet of the primary distillation tower.

[0102] Controlling the operation of the condenser and the reboiler corresponding to the primary distillation tower to obtain the first gas includes:

[0103] Take samples near the discharge port of the primary distillation tower to test the gas purity, and judge whether the gas in the primary distillation tower has reached a state of equilibrium based on whether the gas purity meets the standard;

[0104] If the gas in the primary distillation tower reaches a state of equilibrium, that is, the first gas has been separated from the raw gas, the feed port and the discharge port of the primary distillation tower are opened at the same time, and the feed port of the secondary distillation tower is opened. While the raw gas is introduced into the primary distillation tower, one of the two discharge ports of the primary distillation tower discharges and processes the waste gas, and the other discharges the purified raw gas, that is, the first gas, into the secondary distillation tower through the feed port of the secondary distillation tower.

[0105] For controlling the operation of the condenser and reboiler corresponding to the secondary distillation tower 13 to obtain the second gas, it is similar. By sampling and testing whether the gas purity meets the standard, it is determined whether the separation of the first gas in the secondary distillation tower 13 has reached equilibrium, thereby determining whether the second gas can be obtained.

[0106] It should be noted that after the second gas is obtained, the second gas can be passed through the discharge port of the secondary distillation tower 13 to be stored in the product tank 19, or can be passed into the tertiary distillation tower for further purification and separation.

[0107] Stopping the introduction of the first gas into the secondary distillation tower includes:

[0108] Close the feed inlet and discharge outlet of the secondary distillation tower.

[0109] Control the operation of the condenser and reboiler corresponding to the distillation tower. Taking the primary distillation tower 12 as an example, the condenser is located at the top of the primary distillation tower 12, and the reboiler is located at the bottom of the primary distillation tower 12. The condenser is used to condense the gas at the top of the tower and return it to the middle of the primary distillation tower 12, and the reboiler is used to evaporate and vaporize the liquefied gas at the bottom of the tower and return it to the middle of the primary distillation tower 12. The reboiler and condenser are used as up and down reflux devices, so that the steam and liquid are reversely exchanged on the packing surface of the primary distillation tower 12, so as to realize the exchange and enrichment of various light and heavy components.

[0110] In this embodiment, after the primary distillation tower 12 is in a saturated state, the supply of raw gas to the primary distillation tower 12 is stopped, and the operation of the condenser and the reboiler corresponding to the primary distillation tower 12 is controlled, thereby increasing the amount of raw gas in the primary distillation tower 12 and improving the efficiency of the low-temperature distillation of the primary distillation tower 12; by supplying the first gas with higher purity obtained from the primary distillation tower 12 to the secondary distillation tower 13, after the secondary distillation tower 13 is in a saturated state, the supply of the first gas to the secondary distillation tower 13 is stopped, and the operation of the condenser and the reboiler corresponding to the secondary distillation tower 13 is controlled, so that the second gas with further improved purity can be obtained, and the operation method is simpler and more reliable, which is conducive to being realized through PLC automatic control.

[0111] For some examples, see Figure 2 Before the feed gas is introduced into the primary distillation tower 12, the control method includes:

[0112] S000: Control the adsorption column of the cryogenic distillation system to adsorb gas impurities in the raw gas.

[0113] It should be noted that the adsorption column 11 may be a room temperature adsorption column 11 .

[0114] In this embodiment, part of the gas impurities in the raw gas are removed by the adsorption column 11, so that the purity of the gas entering the primary distillation tower 12 can be improved, thereby improving the efficiency of the cryogenic distillation.

[0115] For some examples, see Figures 1 to 3 , control methods include:

[0116] When the amount of gas filtered by the adsorption column exceeds a preset value or when the feed gas stops passing into the primary distillation tower, the temperature of the adsorption column is controlled to increase so as to regenerate the adsorption column;

[0117] Introduce nitrogen into the adsorption column to bring gas impurities into the absorption tank;

[0118] Collect the temperature signal of the adsorption column and determine whether the temperature signal is within the preset range. If not, output an alarm message.

[0119] It should be noted that when the amount of gas filtered by the adsorption column 11 exceeds a preset value or when the raw gas stops passing into the primary distillation tower 12, it means that the low-temperature distillation system 10 can be regenerated every time the raw gas stops passing into the primary distillation tower 12, that is, when the adsorption column 11 no longer filters the raw gas, or a preset value can be set, and when the amount of gas filtered by the adsorption column 11 exceeds the preset value, the adsorption column 11 is regenerated through PLC control.

[0120] It should be noted that the adsorption column 11 includes two states: operation and regeneration. The room temperature adsorption column 11 does not need to be heated during normal operation. During regeneration, nitrogen is introduced into the adsorption column 11 by switching the valves of the feed port and the discharge port of the adsorption column 11. At the same time, a PWM signal (Pulse width modulation) is output through the analog output channel of the PLC to the solid-state relay to control the heating of the adsorption column 11, thereby achieving the regeneration of the adsorption column 11. The nitrogen introduced into the adsorption column 11 is used as a purge gas and then passes through the high-temperature adsorption column 11 and is discharged into the absorption tank 18, taking away the impurity gas generated after the adsorption column 11 is heated.

[0121] Exemplarily, the heating temperature of the adsorption column 11 is set on the upper computer interface, and a PID (proportional-integral-derivative control, PID control for short) heating control program is written, and a first temperature sensor T1 and a second temperature sensor T2 are respectively provided at the feed port and the discharge port of the adsorption column 11. The temperature signal of the first temperature sensor T1 is used as a temperature control feedback signal, and the temperature signal of the second temperature sensor T2 is used as a temperature alarm signal, so that the temperature signal of the first temperature sensor T1 fluctuates within the set value range, and the temperature signal of the second temperature sensor T2 is used to determine whether a heating abnormality occurs. When the temperature signal of the second temperature sensor T2 exceeds the temperature, the heating function is stopped, and manual judgment and processing are performed.

[0122] In this embodiment, when the amount of gas filtered by the adsorption column 11 exceeds a preset value or when the raw gas stops passing into the primary distillation tower 12, the temperature of the adsorption column 11 is controlled to increase so as to regenerate the adsorption column 11, so that the PLC can automatically control the operation and regeneration of the adsorption column 11, thereby improving the degree of automation of the low-temperature distillation system 10, and the regeneration process is monitored. At the same time, the regeneration of the adsorption column 11 reduces the adhesion of impurity gases on the adsorption column 11, improves the filtering effect of the adsorption column 11 during operation, and thereby improves the purity of the gas entering the primary distillation tower 12.

[0123] For some examples, see Figures 1 to 3 , controlling the primary distillation tower and the secondary distillation tower to be in a preset vacuum state includes:

[0124] Collect vacuum signals from the primary distillation tower and the secondary distillation tower;

[0125] Program the vacuum signal to obtain vacuum data and display the vacuum data;

[0126] Based on the vacuum data, determine whether the primary distillation tower and the secondary distillation tower are in a preset vacuum state.

[0127] It should be noted that the vacuum signal can be collected by a vacuum sensor.

[0128] Exemplarily, vacuum sensors are arranged in the middle and lower parts of the primary distillation tower 12 and the secondary distillation tower 13. The vacuum sensor signal is directly connected to the display instrument, and the instrument output signal is sent to the PLC analog input module through the instrument, and the program conversion is performed according to the exponential function expression, and the vacuum data is displayed on the host computer.

[0129] In this embodiment, by collecting and processing vacuum signals, displaying and storing vacuum data on a host computer, it is possible to provide parameter basis for the control of mechanical pumps and molecular pumps, and to monitor the cryogenic distillation system 10 to improve the stability and reliability of cryogenic distillation.

[0130] For some examples, see Figures 1 to 3 , the process parameter signals collected from the primary distillation tower and the secondary distillation tower include:

[0131] Collecting temperature signals of condensers and / or reboilers corresponding to the primary distillation tower and the secondary distillation tower respectively;

[0132] Collect temperature signals of the primary distillation tower and the secondary distillation tower;

[0133] The process parameter signal is converted by programming to obtain the process parameter data, and the process parameter data is displayed including:

[0134] Controlling the temperature display module to display the temperature signal of the condenser and / or the reboiler;

[0135] Performing programmable conversion on the temperature signal to obtain the temperature data of the condenser and / or the reboiler, and displaying the temperature data of the condenser and / or the reboiler;

[0136] Controlling the thermal resistance module to receive the temperature signals of the primary distillation tower and the secondary distillation tower;

[0137] The temperature signal is converted by programming to obtain the temperature data of the primary distillation tower and the secondary distillation tower, and the temperature data of the primary distillation tower and the secondary distillation tower are displayed;

[0138] Based on the process parameter data, the operating status of the primary distillation tower and the secondary distillation tower is adjusted including:

[0139] Based on the temperature data of the condenser and / or the reboiler, the operating states of the primary distillation column and the secondary distillation column are adjusted.

[0140] It should be noted that when the feed inlet and the discharge outlet of the primary distillation tower 12 and the secondary distillation tower 13 are closed and the gas is separated in the primary distillation tower 12 and the secondary distillation tower 13, the pressure in the primary distillation tower 12 and the secondary distillation tower 13 can be controlled respectively by the temperature of the condensers corresponding to the primary distillation tower 12 and the secondary distillation tower 13.

[0141] It should be noted that the temperature signal is collected in two situations.

[0142] For the temperature signals of important points, an independent low-temperature temperature display module is used for collection, which has higher collection accuracy. After the independent low-temperature temperature display module collects, it communicates with the PLC through the profibus-dp communication module, uploads the temperature signals of important points to the PLC, and displays them on the host computer after programming conversion;

[0143] The temperature signals of other points are directly collected through the thermal resistance module of the PLC and displayed on the host computer after conversion.

[0144] Exemplarily, the important point temperature signals are temperature signals of a condenser and a reboiler.

[0145] Exemplarily, the temperature signal is collected by a temperature sensor, and the temperature sensors all adopt a four-wire connection method, that is, the signal and the power supply are connected separately, which can reduce the interference of the power supply on the temperature signal and improve the precision and accuracy of temperature signal collection.

[0146] Exemplarily, the cryogenic distillation system 10 includes a first condenser 14, a first reboiler 15, a second condenser 16 and a second reboiler 17, which are respectively provided with a third temperature sensor T3, a fourth temperature sensor T4, a fifth temperature sensor T5 and a sixth temperature sensor T6. The first condenser 14 and the first reboiler 15 are respectively arranged at the top and the bottom of the primary distillation tower 12, and the second condenser 16 and the second reboiler 17 are respectively arranged at the top and the bottom of the secondary distillation tower 13. The programmable logic controller controls the temperatures of the first condenser 14 and the first reboiler 15 to reflux materials at the top and the bottom of the primary distillation tower 12 downward and upward, respectively; and controls the temperatures of the second condenser 16 and the second reboiler 17 to reflux materials at the top and the bottom of the secondary distillation tower 13 downward and upward, respectively.

[0147] Exemplarily, a seventh temperature sensor T7 and an eighth temperature sensor T8 are respectively provided at the middle and the bottom of the first distillation tower 12, and the first discharge port of the first distillation tower 12 is provided at the bottom of the first distillation tower 12; a ninth temperature sensor T9 and a tenth temperature sensor T10 are respectively provided at the middle and the bottom of the second distillation tower 13, and the first discharge port of the second distillation tower 13 is provided at the bottom of the second distillation tower 13.

[0148] In this embodiment, by setting temperature sensors at specific points, temperature signals are collected in the cryogenic distillation system 10, which is helpful for auxiliary judgment of the operating status of the primary distillation tower 12 and the secondary distillation tower 13, and at the same time provides data basis for the control of the condenser and the reboiler, which is beneficial for PLC to control the cryogenic distillation system 10.

[0149] In some embodiments, adjusting the operating status of the primary distillation tower and the secondary distillation tower includes:

[0150] Adjust the power of the reboilers corresponding to the primary distillation tower and the secondary distillation tower.

[0151] In some specific embodiments, collecting process parameter signals of the primary distillation tower and the secondary distillation tower includes:

[0152] Collect the liquid level signals of the reboilers corresponding to the primary distillation tower and the secondary distillation tower.

[0153] At the same time, the process parameter signal is converted by programming to obtain the process parameter data, and the process parameter data is displayed including:

[0154] The liquid level signal is converted by programming to obtain the liquid level data and display the liquid level data.

[0155] Based on the process parameter data, the operating status of the primary distillation tower and the secondary distillation tower is adjusted including:

[0156] Adjust the power of the reboilers corresponding to the primary distillation tower and the secondary distillation tower.

[0157] It should be noted that the reboiler power control of the primary distillation tower 12 and the secondary distillation tower 13 both use a three-phase voltage regulator for heating control. The voltage regulator has multiple control modes such as constant pressure, constant current, and constant power. Exemplarily, the present application adopts a constant current mode, and the analog output module of the PLC outputs a 4-20mA current signal to the voltage regulator, corresponding to the 0-25A current of the voltage regulator. After the current is set, the voltage automatically follows the change. The voltage regulator simultaneously outputs the feedback signal of the current current and voltage to the analog input module of the PLC, and the heating current, voltage and power values ​​are displayed on the host computer after programming conversion. The voltage regulator status signals such as running, stopping, overcurrent, circuit breaker, etc. are displayed through the digital output signal to the digital input terminal of the PLC for operation status display.

[0158] Exemplarily, the first reboiler 15 is provided with a first liquid level sensor L1 , and the second reboiler 17 is provided with a second liquid level sensor L2 .

[0159] Here, the power of the reboiler corresponding to the primary distillation tower 12 and the secondary distillation tower 13 is adjusted according to the process parameter data converted from the liquid level signal, so that the power of the reboiler can match the accumulation speed of the liquefied gas at the bottom of the corresponding primary distillation tower 12 and the secondary distillation tower 13, and the reboiler can continuously vaporize the liquefied gas at the bottom, which can improve the stability and safety of the reboiler operation, thereby improving the stability of the cryogenic distillation.

[0160] For some examples, see Figures 1 to 3 The cryogenic distillation system 10 includes a plurality of gas flow controllers, which are arranged at least between the primary distillation tower 12 and the adsorption column 11, between the primary distillation tower 12 and the absorption tank 18, between the primary distillation tower 12 and the secondary distillation tower 13, between the secondary distillation tower 13 and the product tank 19, and between the secondary distillation tower 13 and the absorption tank 18. The absorption tank 18 is used to store nitrogen and gas impurities, and the product tank 19 is used to store the gas obtained after distillation.

[0161] The process parameter signals collected from the primary distillation tower and the secondary distillation tower include:

[0162] Collecting flow signals from each gas flow controller;

[0163] The process parameter signal is converted by programming to obtain the process parameter data, and the process parameter data is displayed including:

[0164] Perform programming conversion on the gas flow signal to obtain gas flow data and display the gas flow data;

[0165] Based on the process parameter data, the operating status of the primary distillation tower and the secondary distillation tower is adjusted including:

[0166] Adjust the gas flow controller.

[0167] Exemplarily, the cryogenic distillation system 10 includes a first branch, a second branch, and a third branch. The first gas outlet of the normal temperature adsorption column 11 is connected to the feed port of the primary distillation tower 12 through the first branch. The first discharge port of the primary distillation tower 12 is connected to the feed port of the secondary distillation tower 13 through the second branch. The second discharge port of the primary distillation tower 12 is connected to the absorption tank 18 through the third branch.

[0168] The cryogenic distillation system 10 also includes a fourth branch and a fifth branch. The first discharge port of the secondary distillation tower 13 is connected to the product tank 19 through the fourth branch, and the second discharge port of the secondary distillation tower 13 is connected to the absorption tank 18 through the fifth branch. The first gas flow controller F1, the second gas flow controller F2, the third gas flow controller F3, the fourth gas flow controller F4 and the fifth gas flow controller F5 are respectively arranged in the first branch, the second branch, the third branch, the fourth branch and the fifth branch. The programmable logic controller adjusts the gas flow of each branch through the flow signal collected by each gas flow controller. In addition, the first branch and the second branch are respectively provided with the eleventh temperature sensor T11 and the twelfth temperature sensor T12 to monitor the gas temperature entering the primary distillation tower 12 and the secondary distillation tower 13 respectively.

[0169] In this embodiment, the gas flow controller communicates with the PLC through the modbus-tcp protocol (full name Modbus Transmission Control Protocol, a communication protocol based on the TCP / IP protocol stack, mainly used to transmit data and commands in the network to achieve communication and control between devices). The gas flow, valve control mode, and cumulative clearing function can be set on the host computer interface. The gas flow controller automatically controls according to the set value to maintain the flow at the set value.

[0170] Exemplarily, the first branch, the first distillation tower 12, the second distillation tower 13 and the product tank 19 are respectively provided with a first pressure sensor P1, a second pressure sensor P2, a third pressure sensor P3 and a fourth pressure sensor P4, and the programmable logic controller adjusts the pressure of the first branch, the first distillation tower 12, the second distillation tower 13 and the product tank 19 through the signals of the first pressure sensor P1, the second pressure sensor P2, the third pressure sensor P3 and the fourth pressure sensor P4.

[0171] Exemplarily, the cryogenic distillation system 10 includes a gas concentration sensor, which is arranged above the raw gas tank and / or above the valve concentration of the cryogenic distillation system 10, and is used to detect the gas concentration in the environment to detect whether there is a gas leak in the system. The pressure, liquid level, and gas concentration sensors output a standard 4-20mA current signal, which is connected to the analog input channel of the PLC after passing through the safety barrier, and is processed by software programming and displayed on the host computer.

[0172] Exemplarily, the cryogenic distillation system 10 includes a refrigeration system, which includes a primary heat exchanger and a secondary heat exchanger. Gaseous methane can exchange heat with liquid nitrogen in the primary heat exchanger. The liquid nitrogen condenses the gaseous methane into liquid methane and transports it to the secondary heat exchanger. The secondary heat exchanger includes a first heat exchanger and a second heat exchanger. The first heat exchanger and the second heat exchanger both have a heat release channel and a heat absorption channel that are not connected to each other. The inlet of the heat absorption channel of the first heat exchanger and the second heat exchanger is used to introduce liquid methane. The inlet and outlet of the heat release channel of the first heat exchanger and the second heat exchanger are respectively connected to the top of the primary distillation tower 12 and the secondary distillation tower 13 to introduce the material to be condensed. The refrigeration system uses liquid methane to achieve heat exchange with the gas at the top of the primary distillation tower 12 and the secondary distillation tower 13 in the first heat exchanger and the second heat exchanger, thereby refluxing the gas at the top of the primary distillation tower 12 and the secondary distillation tower 13 to the middle of the primary distillation tower 12 and the secondary distillation tower 13.

[0173] Exemplarily, the absorption tank 18 is provided with a thirteenth temperature sensor T13 , and the temperature signal collected by the thirteenth temperature sensor T13 is fed back to the PLC to monitor the temperature of the gas introduced into the absorption tank 18 .

[0174] A second aspect of the embodiments of the present application provides a cryogenic distillation control device, which is applied to the control method of the cryogenic distillation system 10 provided in any embodiment of the present application. The cryogenic distillation control device includes:

[0175] A collection module, used to collect process parameter signals of the cryogenic distillation system 10;

[0176] A data conversion module, used for converting a process parameter signal into process parameter data;

[0177] Display module, used to store and display process parameter data, and output alarm signals for abnormal data;

[0178] The regulating module is used to regulate the operation of the primary distillation tower 12 and the secondary distillation tower 13 according to the process parameter data.

[0179] Exemplarily, the cryogenic distillation control device in the present application may include a programmable logic controller (PLC), which is connected to a host computer via a switch, wherein the host computer is used to set parameters, data display, curve display, and data storage of the cryogenic distillation system 10; the PLC is used to collect and monitor various process parameters of the cryogenic distillation system 10 of the present application, and is used to control the cryogenic distillation system 10 of the present application.

[0180] Exemplarily, the host computer program is SIMATIC WinCC (Windows Control Center).

[0181] For example, the cryogenic distillation system 10 can realize the communication between the PLC and the host computer through Ethernet, and realize the functions of process parameter collection and processing, data and curve display, control parameter setting, data storage, signal alarm and interlocking on the host computer interface. When a parameter exceeds the limit, the background color of the parameter changes, and the alarm device drives the sound and light alarm lamp to operate.

[0182] The cryogenic distillation control device provided in the embodiment of the present application is aimed at the existing cryogenic distillation system 10. Through the PLC control system, the process parameters of the primary distillation tower 12 and the secondary distillation tower 13 are monitored in real time and overall controlled, so that the cryogenic distillation system 10 is in a stable working state, the stability of the cryogenic distillation tower is improved, and the cryogenic distillation process requirements are met.

[0183] The various embodiments / implementations provided in this application can be combined with each other without causing any contradiction.

[0184] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A control method for a cryogenic distillation system, based on a programmable logic controller, wherein the cryogenic distillation system comprises a primary distillation tower and a secondary distillation tower, characterized in that: The control method comprises: Controlling the primary distillation tower and the secondary distillation tower to be in a preset vacuum state; Collecting process parameter signals of the primary distillation tower and the secondary distillation tower, wherein the process parameters include at least one of temperature, pressure, flow rate, power, and gas concentration; Performing programming conversion on the process parameter signal to obtain process parameter data, and displaying the process parameter data; Based on the process parameter data, the operating states of the primary distillation tower and the secondary distillation tower are adjusted.

2. The control method of the cryogenic distillation system according to claim 1, characterized in that: Before collecting the process parameter signals of the primary distillation tower and the secondary distillation tower, the control method includes: Passing raw gas into the primary distillation tower; After the primary distillation tower is in a saturated state, stop introducing the raw gas into the primary distillation tower, and control the operation of the condenser and the reboiler corresponding to the primary distillation tower to obtain the first gas; introducing the first gas into the secondary distillation tower; After the secondary distillation tower is in a saturated state, the introduction of the first gas into the secondary distillation tower is stopped, and the operation of the condenser and the reboiler corresponding to the secondary distillation tower is controlled to obtain the second gas.

3. The control method of the cryogenic distillation system according to claim 2, characterized in that: Before the feed gas is introduced into the primary distillation tower, the control method comprises: The adsorption column of the cryogenic distillation system is controlled to adsorb gas impurities in the raw gas.

4. The control method of the cryogenic distillation system according to claim 3, characterized in that: The control method comprises: When the amount of gas filtered by the adsorption column exceeds a preset value or when the feed gas stops passing into the primary distillation tower, controlling the temperature of the adsorption column to increase so as to regenerate the adsorption column; Introducing nitrogen into the adsorption column to bring gas impurities into the absorption tank; The temperature signal of the adsorption column is collected to determine whether the temperature signal is within a preset range, and if not, an alarm message is output.

5. The control method of the cryogenic distillation system according to claim 1, characterized in that: The controlling the primary distillation tower and the secondary distillation tower to be in a preset vacuum state comprises: collecting vacuum signals of the primary distillation tower and the secondary distillation tower; Performing program conversion on the vacuum signal to obtain vacuum data, and displaying the vacuum data; Based on the vacuum data, it is determined whether the primary distillation tower and the secondary distillation tower are in the preset vacuum state.

6. The control method of the cryogenic distillation system according to claim 1, characterized in that: The collecting of process parameter signals of the primary distillation tower and the secondary distillation tower comprises: Collecting temperature signals of condensers and / or reboilers corresponding to the primary distillation tower and the secondary distillation tower respectively; collecting temperature signals of the primary distillation tower and the secondary distillation tower; The step of programming and converting the process parameter signal to obtain process parameter data and displaying the process parameter data comprises: Controlling the temperature display module to display the temperature signal of the condenser and / or the reboiler; Performing programming conversion on the temperature signal to obtain temperature data of the condenser and / or the reboiler, and displaying the temperature data of the condenser and / or the reboiler; Controlling the thermal resistance module to receive the temperature signals of the primary distillation tower and the secondary distillation tower; Performing program conversion on the temperature signal to obtain temperature data of the primary distillation tower and the secondary distillation tower, and displaying the temperature data of the primary distillation tower and the secondary distillation tower; The adjusting the operating states of the primary distillation tower and the secondary distillation tower based on the process parameter data includes: Based on the temperature data of the condenser and / or the reboiler, the operating states of the primary distillation tower and the secondary distillation tower are adjusted.

7. The control method of the cryogenic distillation system according to claim 1, characterized in that: The adjusting the operating states of the primary distillation tower and the secondary distillation tower includes: The powers of the reboilers corresponding to the primary distillation tower and the secondary distillation tower are adjusted.

8. The control method of the cryogenic distillation system according to claim 1, characterized in that: The cryogenic distillation system comprises a plurality of gas flow controllers, which are arranged at least between the primary distillation tower and the adsorption column, between the primary distillation tower and the absorption tank, between the primary distillation tower and the secondary distillation tower, between the secondary distillation tower and the product tank, and between the secondary distillation tower and the absorption tank. The absorption tank is used to store nitrogen and gas impurities, and the product tank is used to store gas obtained after distillation. The collecting of process parameter signals of the primary distillation tower and the secondary distillation tower comprises: Collecting flow signals from each of the gas flow controllers; The step of programming and converting the process parameter signal to obtain process parameter data and displaying the process parameter data comprises: Performing program conversion on the gas flow signal to obtain gas flow data, and displaying the gas flow data; The adjusting the operating states of the primary distillation tower and the secondary distillation tower based on the process parameter data includes: Adjust the gas flow controller.

9. The control method of the cryogenic distillation system according to claim 1, characterized in that: The collecting of process parameter signals of the primary distillation tower and the secondary distillation tower comprises: Collecting liquid level signals of reboilers corresponding to the primary distillation tower and the secondary distillation tower; The step of programming and converting the process parameter signal to obtain process parameter data and displaying the process parameter data comprises: Performing programming conversion on the liquid level signal to obtain liquid level data, and displaying the liquid level data; The adjusting the operating states of the primary distillation tower and the secondary distillation tower based on the process parameter data includes: The powers of the reboilers corresponding to the primary distillation tower and the secondary distillation tower are adjusted.

10. A cryogenic distillation control device, applied to the control method of the cryogenic distillation system according to any one of claims 1 to 9, characterized in that: The cryogenic distillation control device comprises: A collection module, used for collecting process parameter signals of the cryogenic distillation system; A data conversion module, used for converting the process parameter signal into process parameter data; A display module, used to store and display the process parameter data and output an alarm signal for abnormal data; The regulating module is used to regulate the operation of the primary distillation tower and the secondary distillation tower according to the process parameter data.

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